1. Field of the Invention
This invention relates to an amplitude change-over device for a body vibration machine, particularly to one able to change and adjust the strength of amplitude and the value of gravitational acceleration for tallying with a user's requirement in training muscular strength by adjusting a single motor with same frequency to rotate clockwise or counterclockwise.
2. Description of the Prior Art
In reality, our daily activities are affected anytime and anyplace by gravity, and the influence of gravity is a basis for developing our muscular strength. Conventional weight training acted on a human body (gravity Fz) is to employ extra weight and load to be imposed upon the human body. Substantially, human body can naturally enhance its muscular strength to cope with increase of weight and load imposed thereon. Dumbbells and other weight training apparatuses are extra loads for training muscular strength. During taking exercises, a man's body will carry out self-adjustment and correction in accordance with increase of extra loads and hence a man's muscular power can be strengthened and his body will become stronger than ever before.
Compared with conventional weight training, body vibration training does not need extra loads, so it will not be affected by gravity but by acceleration. When an object or a human body changes its velocity in a very short time, assimilation of acceleration will be expanded. According to a formula: Fz (gravity)=m (individual body weight)×a (gravitational acceleration, m/sec.2), when acceleration (a) increases, a body working strength will also be actuated to increase. In comparison with conventional weight training (added with loads), vibration training without extra loads can attain an effect of exercise training faster than the conventional weight training; therefore, body vibration machines used for training a man's muscular power have been widely used.
A conventional body vibration machine 10, as shown in FIGS. 1˜4, includes a standing table 11, an upright post 15, a handrail 16 and a control faceplate 17 combined together.
The standing table 11 is positioned over a base plate 12, and a plurality of buffering and elastic support cylinders 13 are assembled between the base plate 12 and the standing table 11 to connect them together so that when a user stands on the standing table 11, the standing table 11 can produce a buffer effect. The standing table 11 has an intermediate portion of its underside secured with the outer casing of a motor 14, as shown in FIG. 3, and the motor 14 has a rotating shaft 140 with two opposite ends respectively fixed thereon with an eccentric plate 141. Thus, after the motor 14 is started to operate, the two eccentric plates 141 fixed on the opposite ends of the rotating shaft 140 will make the motor 14 produce eccentric vibration, and the standing table 11 secured with the outer casing of the motor 14 will be actuated to vibrate synchronously.
The upright post 15 extending upward is fixedly connected with a front end of the base plate 12.
The handrail 16 and the control faceplate 17 are fixed at the upper end of the upright post 15. When standing on the standing table 11, a user can hold the handrail 16 for supporting and controlling the working conditions of the body vibration machine 10 by means of the control faceplate 17.
In using of the conventional body vibration machine 10, as shown in FIG. 1, after a user stands on the standing table 11 and holds on the handrail 16, the motor 14 is started to operate and, by its eccentric vibration force, driving the standing table 11 to vibrate continuously, and simultaneously the user's body will be actuated to produce continuous vibration, thus achieving effect of exercise training.
However, the conventional body vibration machine 10 can produce only one single amplitude. Under the circumstances, if users of different body conditions need to use different-strength amplitudes, it is necessary to change the extent of the amplitude and for this purpose, the eccentric plate 141 at the opposite ends of the rotating shaft 140 of the motor 14 have to be replaced, thus increasing trouble in disassembling and replacing of the eccentric plates 141 and resulting in inconvenience in use. In another case, if the eccentric plates 141 are not to be replaced, then two motors with different amplitudes have to be used for change of amplitude, thus increasing producing cost and weight of the body vibration machine.